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04/05 Flange defect, take note

If you own a 04 1200GS, go check the flange on your bike, might be 04 and 05 models, just possibly be one of the flanges that will have cracks on the lugs securing the rear brake disc to the flange.

On my 04 1200, the flange which secures the rear wheel and rear brake disc some how got some cracks on all the lugs securing the rear brake disc. It is not a common problem and from the things of it seems to be 04 specific, not confirmed. It is suspected that it is either a design fault or metal fatigue.

This is a safety critical item and on a bike like this must never happen. You need to take of the rear wheel and inspect the flange properly. If you intent buying a 1200GS/GSA let the seller/ dealer take off the rear wheel and confirm it does not have cracks on the lugs as this item will cost you around $280 to replace.

THANKS VERY MUCH

Michnus,
a very big THANK YOU.

Just went out to check my '04 bike. The three 'arms' I could see easily on my rear brake disk/wheel bub were fine (as I expected). Turned the wheel and to my horror, the other two arms have the cracks.

When I recently changed my rear disk due to warping with a tight spot, I did a cursory glance rather than a proper good eyeball. I'm normally a stickler for all things engineering, can't believe I didn't find this earlier (unless its only just occurred).

In hindsight, it may have been the cracked brake disk hub that allowed the disk to warp?

Either way, I'm off to Bahnstormer Motorrad this afternoon on a rideout so will ask them about possible goodwill or discount on a replacement hub. This is not good on a component which is meant to stay together for the life of the bike, and its failure could have potentially life-threatening consequences.

Just went out to check my '04 bike. The three 'arms' I could see easily on my rear brake disk/wheel bub were fine (as I expected). Turned the wheel and to my horror, the other two arms have the cracks.

When I recently changed my rear disk due to warping with a tight spot, I did a cursory glance rather than a proper good eyeball. I'm normally a stickler for all things engineering, can't believe I didn't find this earlier (unless its only just occurred).

In hindsight, it may have been the cracked brake disk hub that allowed the disk to warp?

Either way, I'm off to Bahnstormer Motorrad this afternoon on a rideout so will ask them about possible goodwill or discount on a replacement hub. This is not good on a component which is meant to stay together for the life of the bike, and its failure could have potentially life-threatening consequences.

I did try and read up as much as possible on this, and the general feeling is that it is NOT from over tightening, for one, my brake disc has never been removed from the bike since new. It's either a design fault or material grade.

Perhaps, but I'm pretty sure I would have noticed it. My guess is brittle fracture but as I don't have access to a scanning electron microscope I can't prove it. The profile of the component has no obvious stress raisers and the two cracks have propagated along differing paths.

BMWRich58, I've been an Engineering Technician since 1982. I've worked on Gas Turbines and reciprocating diesels the size of a house and costing millions. I think I can be trusted to safely tighten a fastener or two on a motorbike. Of course I used a torque wrench and followed the instructions in the RepRom, I'm not stupid.

My local dealer has never seen/heard of this happening and took a look out of interest. Eyebrows were raised as the same flange is fitted to the entire R1200 range plus the K1200 model range. They asked if Michnus's bike had the stock disk and pads as mine are non-OEM.

They advised me to contact BMW customer services as a goodwill gesture is unlikely. I simply bit the bullet and ordered a replacement 'flange' under the new part number of C33.11.7.699.631 for £115.99+vat (£133.38) as the old part is no longer available ( I wonder why??).

Pity really as I am unemployed again at present so could do without the (unexpected) expense but my bike is my sole means of transport. No doubt pulling the flange from the splined rear hub will cause me some more headaches. Probably gonna need to put the FD in the freezer for a bit, then get the turbotorch out.

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